The present invention relates to a measuring apparatus for determining the volume of glue in a gluing device of an apparatus, particularly a bottoming or tubing machine, for manufacturing bags and semifinished bag products. The present invention further relates to a gluing device for such an apparatus and a method for determining the volume flow of glue in a gluing device.
It is known to use gluing devices for apparatuses, particularly bottoming or tubing machines, that serve to manufacture bags or semifinished bag products. In such processes, for example material webs are glued to form tubes or tubular webs are cut and the bottoms are laid and glued. In both cases, materials must be glued together. For this, glue must be applied to the material of the bag or semifinished bag product in defined manner and as accurately as possible. Gluing devices are usually equipped with application heads and application valves. This allows the glue to be applied both in the direction of application and to some degree perpendicularly to the direction of application by methods of varying complexity. Such an application device is known for example from International Publication No. WO 2005/002838. In that document, a bottoming device for paper bags is described that produces the bottoms for such paper bags by gluing. For applying the glue, it is important to set the volume flow of the glue as precisely as possible, so that the application, particularly the application thickness of the glue, remains as consistent as possible with a predefined reference value. In known gluing apparatuses in this context, it is typical to use a flowmeter, particularly a flowmeter with a relatively limited measuring range, as the measuring apparatus.
A disadvantage of known gluing devices and the corresponding measuring apparatuses is that they are in direct contact with the glue. Thus, although this offers a relatively accurate option for measuring the desired flow rate, on the other hand the direct measurement of the volume flow rate also entails influencing the flow at least to some degree. In addition, such direct measurement methods of the volume flow typically require relatively expensive sensors. Accordingly, known measuring apparatuses for direct measurement lead to influencing of the volume flow and higher costs.